The invention relates to a polymer mixture which comprises a polyamide, a polyphenylene ether, one or more agents to improve the compatibility of the polyamide and the polyphenylene ether, and an agent to improve the impact strength.
Polymer mixtures which comprise a polyamide, a polyphenylene ether, an agent to improve the compatibility of the polyamide and the polyphenylene ether and optionally an agent to improve the impact strength are known from EP-A 0024120; EP-A 0046040 and EP-A 0147874.
It is stated in EP-A 0024120 that it is desirable to incorporate in the polymer mixtures rubber-like polymers having a high molecular weight to improve the impact strength. By way of example are mentioned inter alia ethylene-propylene, ethylene-propylene-diene copolymers and partially hydrogenated styrene/butadiene block copolymers. There are no examples in which these rubber-like polymers are used. According to EP-A 0024120, a liquid diene compound or an epoxy compound or a compound having a two-fold or three-fold carbon-to carbon bond in the molecular structure and a carboxylic acid, acid anhydride, acid amide, imido, carboxylic acid ester, amino or hydroxyl group is used as an agent to improve the compatibility - in the meaning as will be defined hereinafter.
According to EP-A 0046040 the polymer mixtures described therein may comprise an agent improving the impact strength. In the Specification are mentioned by way of example a) graft polymers obtained by graft polymerization of a monomer which comprises as the main constituent a vinylaromatic compound on a rubber-like polymer and b) thermoplastic elastomers. One graft polymer which is mentioned by name is high-impact polystyrene. As thermoplastic elastomers are mentioned inter alia hydrogenated and non-hydrogenated styrene-butadiene block copolymers and styrene-ethylene-propylene polymers. It is stated that the graft polymer or the thermoplastic elastomer can be used individually or in combination. High-impact polystyrene having a high polybutadiene content and combinations of high-impact polystyrene and a hydrogenated styrene-butadiene block copolymer are used in the examples. One of these agents, notably the hydrogenated styrene-butadiene block copolymer, is generally considered as an agent which is particularly suitable to improve the impact strength of polyphenylene ether or of mixtures of polyphenylene ethers and high-impact polystyrene. The polymer mixtures according to EP-A 0046040 comprise a copolymer with units of a vinylaromatic compound and an alpha-beta dicarboxylic acid anhydride or an imide of an alpha-beta unsaturated dicarboxylic acid as an agent to improve the compatibility.
The polymer mixtures according to EP-A 0147874 may comprise one or more agents to improve the impact strength: mentioned by name as such are high-impact polystyrene, polybutadiene, ethylene-propylene-diene rubbers and hydrogenated or non-hydrogenated thermoplastic rubbers. This Patent Application does not give any examples in which agents improving the impact strength are used. According to this Application, a copolymer with 50-90 mol% units of a vinylaromatic compound and with 41-50 mol% units of an unsaturated dicarboxylic acid or a derivative thereof is used as an agent to improve the compatibility.